In order to stop global warming or the depletion of the ozone layer, various types of substitutes for chlorofluorocarbon have been proposed so far. Hydrofluorocarbons (HFCs), which do not contain chlorine as an element depleting ozone, have been in wide use in order to protect the ozone layer. However, HFCs generally have a long atmospheric life and has a significant influence on the global environment such as global warming and the like.
1-chloro-3,3,3-trifluoropropene (HCFO-1233zd) has geometric isomers, namely, a trans isomer (E isomer) and a cis isomer (Z isomer), which are respectively called “HCFO-1233zd (E)” and “HCFO-1233zd (Z)”. In the case where it is not intended to distinguish whether the isomer is a trans isomer or a cis isomer, the isomer may be referred to as “HCFO-1233zd”. A mixture of the trans isomer and the cis isomer may also be referred to as “HCFO-1233zd”. HCFO-1233zd (E) having a boiling point of 19° C. is commercially produced as a next-generation foaming agent. HCFO-1233zd (Z) having a boiling point of 39° C. is now proposed to be used as a solvent or a washing detergent (Japanese Laid-Open Patent Publication No. 2013-103890).
Like HCFO-1233zd, 2-chloro-1,3,3,3-tetrafluoropentene (HCFO-1224xe) also has a trans isomer (E isomer) and a cis isomer (Z isomer), which are respectively referred to as HCFO-1224xe (E) and HCFO-1224xe (Z). In the case where it is not intended to distinguish whether the isomer is a trans isomer or a cis isomer, the isomer may be referred to as “HCFO-1223xe”. A mixture of the trans isomer and the cis isomer may also be referred to as “HCFO-1223xe”. There are not many documents on HCFO-1223xe. There are not many examples of isolating the trans isomer (E isomer) or the cis isomer (Z isomer), and properties thereof including the boiling point and the like have not been much discussed.
Regarding chlorofluorocarbon and the substitutes for chlorofluorocarbon (hereinafter, referred to as “chlorofluorocarbons”), mixed coolants containing two or more of various chlorofluorocarbons in a mixture have been proposed so far. For example, coolant Nos. R502, R507A, R404A, R407C, R410A and the like of American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) are famous as mixed coolants. These mixed coolants each contain two or more of chlorofluorocarbons mixed at a specific ratio to have a higher coefficient of performance, a higher refrigeration cycle, a higher non-flammability, a lower global warming potential, and the like.
However, the chlorofluorocarbons are volatile. Therefore, if one of the chlorofluorocarbons in such a mixture is evaporated more than the other chlorofluorocarbon(s), the composition ratio of the mixture is changed and thus the properties thereof are changed before the mixture is used. For this reason, it is preferable that the mixture is an azeotropic or azeotropic-like composition, which is volatilized with substantially the same composition ratio as that of a liquid phase. For example, R502 (mixed coolant of R22 and R115) and R507A (mixed coolant of R143a and R125) are each an azeotropic composition, which has exactly the same composition ratio in a gas phase and a liquid phase thereof. These coolants are used as azeotropic coolants. Regarding R410A, the components thereof, namely, R32 and R125, are not azeotropic, but R410A have substantially the same composition ratio in a gas phase and a liquid phase thereof. Therefore, R410A is widely used as an azeotropic-like coolant.
With the current state of the art, it is difficult to find such an azeotropic composition or an azeotropic-like composition theoretically on paper, and needs to be confirmed only by an actual experiment.